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SubjectRe: [resend PATCH v2 11/33] dm: add dax_device and dax_operations support
On Mon, Apr 17, 2017 at 12:09 PM, Dan Williams <dan.j.williams@intel.com> wrote:
> Allocate a dax_device to represent the capacity of a device-mapper
> instance. Provide a ->direct_access() method via the new dax_operations
> indirection that mirrors the functionality of the current direct_access
> support via block_device_operations. Once fs/dax.c has been converted
> to use dax_operations the old dm_blk_direct_access() will be removed.
>
> A new helper dm_dax_get_live_target() is introduced to separate some of
> the dm-specifics from the direct_access implementation.
>
> This enabling is only for the top-level dm representation to upper
> layers. Converting target direct_access implementations is deferred to a
> separate patch.
>
> Cc: Toshi Kani <toshi.kani@hpe.com>
> Cc: Mike Snitzer <snitzer@redhat.com>

Hi Mike,

Any concerns with these dax_device and dax_operations changes to
device-mapper for the upcoming merge window?


> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> drivers/md/Kconfig | 1
> drivers/md/dm-core.h | 1
> drivers/md/dm.c | 84 ++++++++++++++++++++++++++++++++++-------
> include/linux/device-mapper.h | 1
> 4 files changed, 73 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> index b7767da50c26..1de8372d9459 100644
> --- a/drivers/md/Kconfig
> +++ b/drivers/md/Kconfig
> @@ -200,6 +200,7 @@ config BLK_DEV_DM_BUILTIN
> config BLK_DEV_DM
> tristate "Device mapper support"
> select BLK_DEV_DM_BUILTIN
> + select DAX
> ---help---
> Device-mapper is a low level volume manager. It works by allowing
> people to specify mappings for ranges of logical sectors. Various
> diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
> index 136fda3ff9e5..538630190f66 100644
> --- a/drivers/md/dm-core.h
> +++ b/drivers/md/dm-core.h
> @@ -58,6 +58,7 @@ struct mapped_device {
> struct target_type *immutable_target_type;
>
> struct gendisk *disk;
> + struct dax_device *dax_dev;
> char name[16];
>
> void *interface_ptr;
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index dfb75979e455..bd56dfe43a99 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -16,6 +16,7 @@
> #include <linux/blkpg.h>
> #include <linux/bio.h>
> #include <linux/mempool.h>
> +#include <linux/dax.h>
> #include <linux/slab.h>
> #include <linux/idr.h>
> #include <linux/hdreg.h>
> @@ -908,31 +909,68 @@ int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
> }
> EXPORT_SYMBOL_GPL(dm_set_target_max_io_len);
>
> -static long dm_blk_direct_access(struct block_device *bdev, sector_t sector,
> - void **kaddr, pfn_t *pfn, long size)
> +static struct dm_target *dm_dax_get_live_target(struct mapped_device *md,
> + sector_t sector, int *srcu_idx)
> {
> - struct mapped_device *md = bdev->bd_disk->private_data;
> struct dm_table *map;
> struct dm_target *ti;
> - int srcu_idx;
> - long len, ret = -EIO;
>
> - map = dm_get_live_table(md, &srcu_idx);
> + map = dm_get_live_table(md, srcu_idx);
> if (!map)
> - goto out;
> + return NULL;
>
> ti = dm_table_find_target(map, sector);
> if (!dm_target_is_valid(ti))
> - goto out;
> + return NULL;
>
> - len = max_io_len(sector, ti) << SECTOR_SHIFT;
> - size = min(len, size);
> + return ti;
> +}
>
> - if (ti->type->direct_access)
> - ret = ti->type->direct_access(ti, sector, kaddr, pfn, size);
> -out:
> +static long dm_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
> + long nr_pages, void **kaddr, pfn_t *pfn)
> +{
> + struct mapped_device *md = dax_get_private(dax_dev);
> + sector_t sector = pgoff * PAGE_SECTORS;
> + struct dm_target *ti;
> + long len, ret = -EIO;
> + int srcu_idx;
> +
> + ti = dm_dax_get_live_target(md, sector, &srcu_idx);
> +
> + if (!ti)
> + goto out;
> + if (!ti->type->direct_access)
> + goto out;
> + len = max_io_len(sector, ti) / PAGE_SECTORS;
> + if (len < 1)
> + goto out;
> + nr_pages = min(len, nr_pages);
> + if (ti->type->direct_access) {
> + ret = ti->type->direct_access(ti, sector, kaddr, pfn,
> + nr_pages * PAGE_SIZE);
> + /*
> + * FIXME: convert ti->type->direct_access to return
> + * nr_pages directly.
> + */
> + if (ret >= 0)
> + ret /= PAGE_SIZE;
> + }
> + out:
> dm_put_live_table(md, srcu_idx);
> - return min(ret, size);
> +
> + return ret;
> +}
> +
> +static long dm_blk_direct_access(struct block_device *bdev, sector_t sector,
> + void **kaddr, pfn_t *pfn, long size)
> +{
> + struct mapped_device *md = bdev->bd_disk->private_data;
> + struct dax_device *dax_dev = md->dax_dev;
> + long nr_pages = size / PAGE_SIZE;
> +
> + nr_pages = dm_dax_direct_access(dax_dev, sector / PAGE_SECTORS,
> + nr_pages, kaddr, pfn);
> + return nr_pages < 0 ? nr_pages : nr_pages * PAGE_SIZE;
> }
>
> /*
> @@ -1437,6 +1475,7 @@ static int next_free_minor(int *minor)
> }
>
> static const struct block_device_operations dm_blk_dops;
> +static const struct dax_operations dm_dax_ops;
>
> static void dm_wq_work(struct work_struct *work);
>
> @@ -1483,6 +1522,12 @@ static void cleanup_mapped_device(struct mapped_device *md)
> if (md->bs)
> bioset_free(md->bs);
>
> + if (md->dax_dev) {
> + kill_dax(md->dax_dev);
> + put_dax(md->dax_dev);
> + md->dax_dev = NULL;
> + }
> +
> if (md->disk) {
> spin_lock(&_minor_lock);
> md->disk->private_data = NULL;
> @@ -1510,6 +1555,7 @@ static void cleanup_mapped_device(struct mapped_device *md)
> static struct mapped_device *alloc_dev(int minor)
> {
> int r, numa_node_id = dm_get_numa_node();
> + struct dax_device *dax_dev;
> struct mapped_device *md;
> void *old_md;
>
> @@ -1574,6 +1620,12 @@ static struct mapped_device *alloc_dev(int minor)
> md->disk->queue = md->queue;
> md->disk->private_data = md;
> sprintf(md->disk->disk_name, "dm-%d", minor);
> +
> + dax_dev = alloc_dax(md, md->disk->disk_name, &dm_dax_ops);
> + if (!dax_dev)
> + goto bad;
> + md->dax_dev = dax_dev;
> +
> add_disk(md->disk);
> format_dev_t(md->name, MKDEV(_major, minor));
>
> @@ -2781,6 +2833,10 @@ static const struct block_device_operations dm_blk_dops = {
> .owner = THIS_MODULE
> };
>
> +static const struct dax_operations dm_dax_ops = {
> + .direct_access = dm_dax_direct_access,
> +};
> +
> /*
> * module hooks
> */
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index a7e6903866fd..bcba4d89089c 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -130,6 +130,7 @@ typedef int (*dm_busy_fn) (struct dm_target *ti);
> */
> typedef long (*dm_direct_access_fn) (struct dm_target *ti, sector_t sector,
> void **kaddr, pfn_t *pfn, long size);
> +#define PAGE_SECTORS (PAGE_SIZE / 512)
>
> void dm_error(const char *message);
>
>

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